I'm glad that worked out, so I guess you had to explicitly set 'auto' on IE6 in order for it to mimic other browsers!
I actually recently found another technique for scaling images, again designed for backgrounds. This technique has some interesting features:
The markup relies on a wrapper element:
<div id="wrap"><img src="test.png" /></div>
Given the above markup you then use these rules:
#wrap {
height: 100px;
width: 100px;
}
#wrap img {
min-height: 100%;
min-width: 100%;
}
If you then control the size of wrapper you get the interesting scale effects that I list above.
To be explicit, consider the following base state: A container that is 100x100 and an image that is 10x10. The result is a scaled image of 100x100.
So, in other words, the image is always at least as big as the container, but will scale beyond it to maintain it's aspect ratio.
This probably isn't useful for your site, and it doesn't work in IE6. But, it is useful to get a scaled background for your view port or container.